Endodermal sinus tumor (yolk sac tumor) of the ear

Endodermal sinus tumors (yolk sac tumors) are malignant germ cell tumors that usually arise in the gonads. We report what is, to our knowledge, the first known case of an endodermal sinus tumor of the ear. The tumor was present in a developmentally delayed child with an abnormal temporal bone and exhibited histopathologic and immunocytochemical features identical to those of endodermal sinus tumors of gonadal origin. The tumor resolved after chemotherapy, and the patient remained alive without evidence of disease at the time of this writing. The purpose of this report is to add a rare tumor to the differential diagnosis of neoplasms of the ear in children and to familiarize otorhinolaryngologists and head and neck surgeons with its pathologic features and clinical management.